the C programming language 练习

p13 ，练习1-9

连续空格用一个代替

#include 

void main()
{
	int c = getchar();
	int lastc = 0;
	while (c != '\n')
	{
		if ((c!=' ') || (lastc!=' '))	//输出字符的条件集合
			putchar(c);
		lastc = c;
		c = getchar();
	}
	putchar('\n');
}

p15 ，练习1-12

每行一个单词输出

使用符号常量

#include 

#define IN 1
#define OUT 0

void main()
{
	int c = 0;
	int state = OUT;
	while ((c=getchar()) != '\n')
	{
		if (c==' ' || c=='\t')
		{
			if (state == IN)
			{
				putchar('\n');
				state = OUT;
			}
		}
		else if (state == OUT)
		{
			state = IN;
			putchar(c);
		}
		else 
			putchar(c);
	}
	putchar('\n');
}

p15~16 ，示例代码

统计各数字，空白符，其他字符数

多路判定：

if
else if
……
else

代码：

#include 

void main()
{
	int c = 0;
	int i = 0;
	int nwhite = 0;
	int nother = 0;
	int ndigit[10];
	for (i = 0; i < 10; i++)
		ndigit[i] = 0;

	while ((c = getchar()) != '\n')
	{
		if (c >= '0' && c <= '9')
			ndigit[c-'0']++;
		else if (c==' ' || c=='\t')
			nwhite++;
		else
			nother++;
	}

	printf("digit =");
	for (i = 0; i < 10; i++)
		printf(" %d", ndigit[i]);
	printf("\nwhite space = %d\nother = %d\n", nwhite, nother);
}